1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic process, and relates to an image forming apparatus such as a copying machine, a printer or a facsimile machine.
2. Related Background Art
Speeding up, sophistication and colorization of an image forming apparatus using an electrophotographic process have been recently advanced, and a copying machine, a printer and a facsimile machine adopting various modes have been used.
Among others, an image forming apparatus adopting an in-line mode, in which image forming units for forming toner images having multiple different colors are arranged in parallel in a direction for conveying a transfer material born by a transfer belt as transfer material bearing members and the toner images are sequentially multi-transferred from a plurality of the image bearing members to the transfer material, can form an image at a high speed, and hence it can be considered to be a main product in future. Besides such an image forming apparatus, there is also proposed a process, in which image forming units for forming multiple different color toner images are arranged in parallel in a direction along which an intermediate transfer belt as an intermediate transfer member moves and the toner images are sequentially multi-transferred from a plurality of image bearing members to the intermediate transfer member so that the toner images on the intermediate transfer belt are then collectively transferred on the transfer member.
In such an image forming apparatus, when the toner remains on or adheres to the surface of the transfer belt or the intermediate transfer belt, this can be a cause of an defective image unless any type of cleaning is carried out to remove such toner. There is proposed a cleaning device in which a blade for scraping off the toner remaining on or adhered to the surface of the transfer belt or the intermediate transfer belt in contact with the transfer belt or the intermediate transfer belt is disposed so that the scraped-off unnecessary toner is collected in a waste toner tank.
Further, there is also proposed an image forming apparatus such that the process cartridge having at least the image bearing member, the cleaning device and the waste toner tank is integrally constituted and the process cartridge can be attached to or detached from the apparatus main body. This structure is adopted in order to facilitate the replacement by a user when the life duration of the image bearing member is ended. In such an image forming apparatus, since the waste toner tank can be also replaced when changing the process cartridge, this apparatus is superior in the usability.
Furthermore, there is also proposed a system by which the toner adhered to the transfer belt or the intermediate transfer belt is electrostatically transferred to one specific image bearing member among a plurality of image bearing members each time without using the above-described cleaning device for scraping off the toner adhered to the transfer belt or the intermediate transfer belt and the transferred toner is collected by a cleaning device for the image bearing member.
In the above-described image forming apparatus, since the toner remaining on or adhered to the transfer material bearing member or the intermediate transfer member has the electrostatic charge of a normal charging polarity as well as the electrostatic charge of the polarity which is opposite from the above polarity and no electrostatic charge at all by an effect of a transfer electric field or the like, the toner remaining on or adhered to the transfer material bearing member or the intermediate transfer member is unable to be completely transferred to the specific image bearing member to be collected. Consequently, a fouling back of the transfer material or a defective image might occur.
Further, in the above-described image forming apparatus using the plural image bearing members, the toner remaining on or adhered to the transfer material bearing member or the intermediate transfer material is collected in the waste toner tank of the cleaning device for a specific image bearing member, which degrades the efficiency of use of the waste toner tank. That is, the waste toner tank for the specific image bearing member becomes full excessively earlier than the waste toner tank of any other image bearing member, and the waste toner tank must be frequently replaced, thereby lowering the usability.
In addition, in an image forming apparatus having a plurality of the process cartridges, since the waste toner tank of the cleaning device provided in a specific process cartridge becomes full excessively earlier before the unspent toner accommodated in the specific process cartridge is completely used up or before the life duration of a photosensitive drum is expired, the process cartridge must be replaced with a new one or a replacement timing of the specific process cartridge comes excessively earlier than that of any other process cartridge.
It is an object of the present invention to provide an image forming apparatus capable of excellently cleaning the toner on a moving member.
Other objects of the present invention will be understood in conjunction with the following detailed description.